In inkjet printing technology, solutions of hole transport material such as PEDOT/PSS (doped polyaniline), and materials emitting red, green and blue light are respectively sprayed into a sub-pixel pits of a substrate on which a patterned metal electrode (for example, a anode) has been previously disposed, by a micron-sized printing nozzle, thereby forming light emitting pixel units having three primary colors of red, green and blue.
The hole injection materials and the hole transport materials cooperated with the currently used light emitting materials of three colors of red, green and blue are different, and it is difficult to unify the hole injection materials and the hole transport materials cooperated with the light emitting materials of three colors into the same material due to the problem of matching of the energy levels. The light emitting materials of three colors of red, green and blue need to use three nozzles, and the printing of the nozzles need to be programmed separately, which brought difficulties to the implementation of inkjet printing, and further brought printing results due to a variety of unstable factors.